package day.day6_29;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        while(sc.hasNext()){
            int a=sc.nextInt();
            int b=sc.nextInt();
            int c=sc.nextInt();
            int d=sc.nextInt();
            //通过运算得到A,B,C的值
            int A=(a+c)/2;
            int B1=(b+d)/2;
            int B2=(c-a)/2;
            int C=(d-b)/2;
            //此处只需要判断B1和B2是否一样即可
           if (B1!=B2){
               System.out.println("No");
           }else{
               System.out.println(A+""+B1+""+C);
           }
        }
    }
}
